This invention relates generally to hand tools. More particularly, the present invention relates to an improved composite handle and means for attaching the handle to the heads of percussive tools, such as hammers, hatchets, axes and the like, in such a manner that the union will be strong and invariable during the normal useful life of the tool, and which may be utilized equally well during the original manufacture of the the tool or while replacing the handle in the field.
Until recent years the only material used for handles in percussive tools, i.e., striking, cutting and/or prying tools such as hammers, sledges, peaveys, axes, etc., has been wood. For this reason, the method of attaching the handle to the tool head, whatever type it might have been, was dictated by the property characteristics of wood. It is generally recognized that, other than being strong enough to withstand handle abuse the tool would regularly take, there are two conditions which must be accommodated when inserting a wood handle into a tool head: to keep the tool head attached to the handle under all working conditions; and to maintain the head tight to the handle.
Traditionally, in percussive tools such as sledge hammers, the tool head includes an aperture or eyehole through its body which has a single or double taper. In both cases, the taper expands at the top of the tool head or that portion which is normally directed away from the user when the tool is in use. When a wooden handle is driven through the eyehole from the bottom side of the tool head, the excess wood protruding from the top side is cut off, and some wedging device, such as an ordinary wedge, is driven into the wood so that the upper end thereof is expanded to provide an inverted frustum which, theoretically, is tightly expanded into the tool eyehole. The expanded section of wood must fit within the upper tapered portion of the eyehole tightly so that the head cannot fly off during use. This is a very elemental assembly which has been in use for many years.
The use of wedges and the like to expand the upper section of the wood within the eyehole inherently involves damage to the handle which adversely affects many of the physical properties which are desired to be retained. Further, the wedges that are driven into the end of the wooden handle often tend to work loose, due most frequently to changes in humidity which cause alternate swelling and contraction of the wood with a gradual decrease in tightness. Many expedients have been employed in an attempt to overcome these faults, including the provision of metal sleeves to hold the tool handle in place, the use of adjustable wedges which must be periodically driven by the owner of the tool to compensate for loosening of the joint, the use of metal handles, the casting of wedges in position in the tool, and the provision of rubber sleeves interposed between the handle and the head. None of these aforementioned expedients have proven to be entirely satisfactory.
The primary reason why prior handles are typically inserted from the bottom and wedged at the top of the tool head is that there are very few tools which have an eyehole large enough to provide an opening through which the grip of the handle can pass. In prior handles, if the handle were small enough to pass through the eyehole, the grip would be much too small for a man to properly grasp it, and the wood would be too small to resist the abuse that the tool would take. Notably, there is one category of percussive tools that does not require the handle to be inserted from the bottom and then affixed within the eyehole as described above. This category includes the pick or pick-mattock style of tool in which the eyehole is so massive that even a large grip can be passed through the eyehole. Traditionally the handles for such pick or pick-mattock style tools are shaped so that the upper end has a reverse taper allowing the pick to be dropped over the grip onto the end farthest away from the user so that the expanded end of wood is large enough to lock the tool head in place and prevent it from ever sliding off the upper end. Of course, the tool head can always be removed in the same manner it is placed on the handle, by removing it from the butt or grip end.
Recent years have seen the development of extremely strong composite tool handles formed of reinforcing fibers cured within a resin composite. Such reinforcing fibers may include fiberglass, polyester, boron, kevlar or graphite, and suitable resin composites include polyester, epoxy, phenolics, etc. With the development of these composite materials, the shaft underneath the tool head can now be made with a cross-section small enough to pass through the conventional eyehole of percussive tool heads, yet have sufficient strength to withstand the tremendous impact forces to be applied.
As advanced materials have been introduced to replace wood, the materials have been either bonded into the eyehole of the tool, substituting the bond for the old traditional wedge, and/or welded such as metal to metal. Whereas these techniques are suitable to some degree for the manufacture of original tools in which the handle is installed with appropriate machinery and equipment at a factory, the techniques are not suitable when practiced in the field. In the case of bonding, composite shafts have been attached to tool heads primarily by means of adhesives in the epoxy field. When utilizing such adhesives, despite the continued development of these materials, it takes care, precision and good workmanship to properly install a replacement handle in a tool head, reliably in the field with no secondary tools to assist. Even in factories where the tool head is installed on a production basis, high levels of quality control must be practiced in order to insure that the head is secured to the handle under all anticipated working conditions. Further, since the high strength composite shafts are usually inadequate in cross-sectional size to be comfortable for a user's hands, a grip of rubber or some other plastic material is usually molded onto the shaft or subsequently bonded thereto in a manner which guarantees that the grip will not accidentally slide off the shaft.
Accordingly, there has been a need for a highly reliable, simplified method by which a handle can be installed onto a percussive tool head, in which the handle is permitted to pass through the eyehole from the upper end in a manner which effectively prohibits the tool head from flying off the handle unintentionally. A handle for use in such method must include a minimum number of separate parts in order to greatly simplify assembly of the handle to the tool head, and also permit attachment of a grip which comfortably fits a user's hands. Further, an improved method of attaching a handle to a percussive tool is needed which facilitates use of reinforced composite tool handles as field replacements for older tools, which overcomes drawbacks associated with fixing such handles within the eyehole of the tool head solely by means of an epoxy. Moreover, an improved tool handle and method of attaching the handle to a percussive tool is needed which simplifies the manufacture and assembly of tools for both a field user and original equipment manufacturers. The present invention fulfills these needs and provides other related advantages.